1. Field of the Invention
The invention relates to a process cartridge detachably mountable to an image forming apparatus, and to an image forming apparatus.
Herein, the image forming apparatus is an apparatus for forming an image on a recording medium such as recording paper, an OHP sheet, or cloth by the use of an electrophotographic image forming process, and covers, for example, an electrophotographic copying machine, an electrophotographic printer (such as an LED printer or a laser beam printer), a facsimile apparatus and a word processor.
The term “process cartridge” refers to an electrophotographic photosensitive drum and at least one process means for acting on the electrophotographic photosensitive drum integrally made into a cartridge detachably mountable to the main body of the image forming apparatus, or an electrophotographic photosensitive drum and at least developing means integrally made into a cartridge detachably mountable to the main body of the image forming apparatus. The process means include, in addition to developing means for supplying a developer to the electrophotographic photosensitive drum, charging means for charging the electrophotographic photosensitive drum, cleaning means for cleaning the electrophotographic photosensitive drum, etc.
2. Description of Related Art
In an image forming apparatus using the electrophotographic image forming process, selective exposure is effected on an electrophotographic photosensitive drum (hereinafter simply referred to also as the photosensitive drum) uniformly charged by charging means to thereby form a latent image on the surface of the photosensitive drum. The latent image is then visualized by a developer supplied from developing means, and thereafter the visualized image is transferred to a recording medium and further, the image is fixed by heat and pressure or the like to thereby effect image recording on the recording medium.
Also, any residual developer on the photosensitive drum after the transfer is removed by cleaning means, such as a cleaning blade and is contained as a removed developer in a cleaning container and therefore, the next development operation can be effected without any residual developer remaining on the surface of the photosensitive drum.
There has been adopted a process-cartridge system whereby of these portions concerned with image formation, the photosensitive drum and the process means (such as the charging means, the developing means and the cleaning means) for acting on the photosensitive drum are integrally made into a cartridge, which is made detachably mountable to the main body of the image forming apparatus. In this case, a user himself can effect the interchange of the cartridge to thereby interchange the photosensitive drum and consumables, such as the developer, without maintenance by a serviceman.
As the construction of an image forming apparatus for forming a multicolor (color) image by the use of such a process cartridge, a plurality of process cartridges containing developers of different colors therein are arranged in parallel to thereby constitute an image forming portion.
The process cartridge of this type may be left outside the main body of the image forming apparatus, or even if it is mounted in the main body of the image forming apparatus, the openable and closable door of the main body of the apparatus may sometimes be opened. In such a state, the photosensitive drum of the process cartridge may be exposed to external daylight and a characteristic thereof may deteriorate. Also, in case of the handling of the process cartridge outside the main body of the apparatus, the process cartridge may be damaged or foreign substances may adhere to the surface of the photosensitive drum. In order to eliminate the possibility of such deterioration or damage, there is provided a shutter member functioning as a protective member for protecting an exposed portion of the photosensitive drum, which is exposed out of a cartridge frame. When the process cartridge is outside the main body of the apparatus, the shutter member is closed, and when the process cartridge is mounted in the main body of the apparatus, the shutter member is opened to thereby expose the photosensitive drum, and during the operation of the image forming apparatus, it is retracted to a position in which it does not hamper image formation.
Now, in the image forming apparatus, in recent years, there has been a strong desire for the downsizing of the image forming apparatus on the part of the user, and there has been the problem that it is difficult to secure a great stroke for opening and closing the shutter member. There has further been a strong desire for the simple mounting and dismounting of the process cartridge, and it has been necessary to open and close the shutter member in operative association with the mounting and dismounting of the process cartridge. Moreover, the provision of a complicated mechanism on the opening and closing means of the shutter member leads to an increase in the cost of parts and the failure rate and therefore, it has been necessary for the opening and closing means to be a simple mechanism.
Further, in a full-color image forming apparatus of the in-line type, process cartridges of respective colors must be disposed in a limited space, and with regard also to the retraction position and retraction path of the shutter member of the photosensitive drum, the limitation in space is great. Also, not only in the full-color image forming apparatus, but also from the viewpoint of space saving, it is desirable that the space necessary for the retraction of the shutter member of the photosensitive drum be as small as possible.